Out of all the MMOs I've played, especially comparing to WoW, the CC in SWTOR is mild. The WoW diminishing returns system is way worse than resolve, nearly EVERY class in WoW now has a stun, root, slow, etc... In swtor most classes have 1 or 2 of these. Resolve allows you some form of control, to use your trinket efficiently, waiting to pop all your crap during resolve. You gotta take advantage of it. Diminishing returns, especially in battlegrounds, is uncontrollable. It's very frustrating. If I'm an operative and I see a player is nearly at full resolve, I'll pin down then save my stun. In WoW, you'll walk up to stun someone in a BG and find it lasts 1 second, congrats you wasted your stun.
I used to be a resolve/CC SWTOR hater, but playing WoW with a scroll of rez made me appreciate the system lol. The only problem I have is with the annoyance of pulls/knockbacks which WoW has very little of (but again, it has 2x the roots, stuns, and slows). Roots need to contribute just a tad to resolve, maybe 1/5 of the bar.